This invention relates to a remote control receiver for the reception of command signals having different frequencies each associated with a particular command function, and responsive thereto to generate an appropriate signal at a corresponding output channel of the receiver.
One such receiver is described in U.S. Pat. No. 3,855,575 issued Dec. 17, 1974, to Horst Leuschner et al. and assigned to Texas Instruments Incorporated, for "Ultrasonic Remote Control Receiver". In that receiver, an incoming ultrasonic command signal is converted to square wave pulses of the same frequency, the pulses then being counter over a fixed period of time. The circuit for determining the duration of the measuring period must be accurately adjusted prior to operation of the receiver so that the desired counting results actually will be achieved when counting the received command signals.
An alternative remote control receiver is disclosed by copending application Ser. No. 681,949 filed April, 1976 by Horst Leuschner and Lembit Soobik for REMOTE CONTROL RECEIVER. In that receiver, a command signal frequency counter counts a predetermined number of command signal cycles. An output signal from the command signal frequency counter controls a reference frequency counter so that the latter counts reference frequency cycles for the period of time during which the predetermined number of command signal cycles is received. The reference frequency counter count reached after the reception of the predetermined number of command signal cycles, therefore, is directly related (inversely proportional) to the command signal frequency received. The count of the reference frequency counter reached in one counting cycle of the command signal counter can be stored in a storage device whose content is then compared by a comparator circuit with the new reference frequency counter count reached after each counting cycle of the command signal frequency counter. The output signal of the comparator circuit indicating agreement or non-agreement of the compared values is supplied to an error register arrangement which releases a control signal at the receiver output associated with the particular command signal received, only after a predetermined number of uninterrupted subsequent agreements of the compared values has been achieved.
Such a receiver is advantageous in that, for example, the minimum counting cycle duration can be considerably reduced compared with the measurement time required to count a succession of incoming command signals by a receiver as described in U.S. Pat. No. 3,855,575. Additionally, this alternative form of receiver is operable by command signal frequencies which are an integer fraction of a fixed reference frequency and thus readily generated by a programmable divider.